GPS multi-path signal reception

• US 5,592,174 A
• Filed: 01/26/1995
• Issued: 01/07/1997
• Est. Priority Date: 01/26/1995
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Nelson, George F.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/378,436
• Time in Patent Office: 712 Days
• Field of Search: 342/357, 343/848, 343/841, 343/700 MS, 343/851, 343/844, 343/846
• US Class Current: 342/357.64
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H01Q 1/521 reducing the coupling between adjacent antennas
• CPC Class Codes: H01Q 17/001 for modifying the directional characteristic of an aerial

Abstract

A pair of GPS receivers A and B which are constructed in the form of the receiver antenna combinations with receivers/antenna combinations which have been associated as ground-planes that extend beyond them. They are arranged such that the lower surface of the ground-plane of one receiver is adjacent to an RF absorber sheet, and the bottom of the RF absorber sheet is placed from the top of the second GPS receiver. This structure allows for the mask angle of the GPS receiver B to be matched to the mask angle of the GPS receiver A. When the normal path signal received by GPS receiver A becomes so large that it interferes with the direct signal to an unsatisfactory degree, reception is switched to GPS receiver B which senses only multi-path signals, but which allows the lock of the receiver pair combination to be maintained.

Claims

1. A Global Positioning System (GPS) for receiving satellite positioning signals comprising,

a first signal-locking receiver for locking-in on said satellite positioning systems,

a first ground plane located adjacent to said first receiver, the periphery of which extends beyond the periphery of said first receiver, and

RF absorber positioned adjacent said first ground plane and having a periphery substantially coextensive with the periphery of said first ground plane,

a second signal-locking receiver located so that an RF absorber is positioned intermediate said first ground plane and said second receiver, and a second ground plane located adjacent said second receiver such that said second receiver is positioned intermediate said second ground plane and said RF absorber, said first and second receivers constructed to have a direct receiving angle for receiving direct positioning signals from said satellites and a multi-path receiving angle for receiving positioning signals that are reflected off of objects and, thereby, indirectly received by said first and second receivers through said multi-path receiving angles, wherein said second receiver is spaced from said RF absorber such that said RF absorber blocks direct positioning and multiple reflections between ground plane signals while providing a multi-path receiving angle for said multi-path receiving signals, and said first receiver will lock in on said direct signals when it exceeds a lock-in threshold, and said second receiver will lock in on said multi-path signal when said direct signal is less than said lock-in threshold.

2. A GPS system as claimed in claim 1 wherein said first and second receivers are constructed as circular-shaped disks.

3. A GPS system as claimed in claim 2 wherein said first and second ground planes and said RF absorber are constructed as circular-shaped disks.

4. A GPS system as claimed in claim 3 wherein said multi-path receiving angle of said second receiver is defined by a first surface that runs between the outer edges of the lower surface of the RF absorber and the outer edges of the upper surface of the second receiver and a second line that runs along the upper surface of said second ground plane.